In general, wireless communications systems using beamforming make use of a number of transmit and/or receive antennas and signal processing to create fixed or adaptive transmit/receive beampatterns. The beampatterns may have a directional nature that may result in a performance improvement when compared with unidirectional transmit and/or receive antennas. The use of the beampatterns may yield a transmit/receive gain over wireless communications systems using unidirectional transmit and/or receive antennas.
In addition to increased computational requirements arising from the signal processing, wireless communications systems that use beamforming require multiple transmit and/or receive antenna. With each transmit and/or receive antenna, there is a number of electronic circuitry and components required to support the antenna, with a power amplifier (PA) used to amplify a signal to be transmitted and high-power signal cabling used to connect the PA to an antenna potentially being the most expensive. For example, the high-power signal cabling may be on the order of several inches in diameter to minimize signal loss.
The sheer physical size and weight of the high-power signal cabling may also present a problem with implementation. Typically, a communications tower may be owned by a tower company and leased to one or more service providers who install their communications equipment on and around the communications tower. Usually, a communications tower may be rated by weight loading and wind loading factors. Therefore, a communications tower may be capable of supporting a finite number of antennas, high-power signal cables, and so forth. For example, a communications tower may be capable of supporting 18 high-power signal cables. However, since the communications tower may be leased to three or more service providers, each service provider may only have six (6) high-power signal cables on the communications tower. Furthermore, given that most communications systems use sectored antennas (with three sectors being a commonly used number), each service provider may only have two high-power signal cables per sector. This may restrict the service provider to having only two transmit/receive antennas per sector or one transmit and one receive antenna per sector, which may limit the service provider's ability to use beamforming.
Therefore, there is a need to provide beamforming like performance improvements while minimizing the number of antennas, PAs, high-power signal cabling, and so forth, to reduce costs. Furthermore, by minimizing the number of antennas, PAs, high-power signal cabling, and so forth, existing communications towers may be used, further reducing the cost of implementing a wireless communications system.